. Adventures with animals and plants. Biology. PROBLEM 4. Hoiv Flams Respond to Swimli ".o<;. Fig. 283 Mimosa, or Sensitive Plant. When the photograph at the left ivas taken, the plant had been undisturbed for several hours. The whole plant was slightly jarred and, after a few 7mnutes, again photographed. Which parts responded to the stivmlus? How is the response fnade? (general biological supply) them. See Figure 284. The pitcher plant, common in many swamps, is also an in- sect-eating plant but it merely traps in- sects without directly responding to their touch. Once the insect is c
. Adventures with animals and plants. Biology. PROBLEM 4. Hoiv Flams Respond to Swimli ".o<;. Fig. 283 Mimosa, or Sensitive Plant. When the photograph at the left ivas taken, the plant had been undisturbed for several hours. The whole plant was slightly jarred and, after a few 7mnutes, again photographed. Which parts responded to the stivmlus? How is the response fnade? (general biological supply) them. See Figure 284. The pitcher plant, common in many swamps, is also an in- sect-eating plant but it merely traps in- sects without directly responding to their touch. Once the insect is caught all these plants secrete juices which digest the prey. Animal and plant behavior. Animals and plants have little in common in their behavior. This is to be expected since their structure is so different. But they have one thing in common. They are liv- ing, that is, they consist of protoplasm which is irritable. Therefore, they all re- spond to stimuli in the environment, even though the stimuli may be very different. Plants, in general, have a large variety of tropisms. Parts of the plant turn to- ward or away from a variety of stimuli such as light, gravity, water, and chem- icals. Certain plants, such as the tulip in its "sleep" movements, the insect- eating plants, and some others have re- sponses other than tropisms, but these are the exceptions. Plants have nothing like a nervous system nor even nerve cells. Plant responses are slow because movements toward or away from the source of a stimulus are by unequal growth on opposite sides of the stem or root, or by changes in turgidity of cells. When it is a matter of growth, it takes hours (or days) for the response to be- come evident. The growth hormones, or auxins, play a part in such movements. As you can see, behavior in plants is far simpler than behavior in all but the simplest animals. Since plants lack a nerv- ous system, and lack even nerve cells, they cannot have the variety of responses shown by an
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